The present invention relates generally to the art of electromagnetic skin treatment, including devices and methods for removing hair. The invention relates to a method and apparatus for utilizing a spatially dispersed or extended pulsed light source such as a flashlamp and providing treatment parameters for its use, and also relates to use of devices and methods that utilize electromagnetic energy to kill hair follicles.
It is known in the prior art to use electromagnetic radiation in medical applications for therapeutic uses such as treatment of skin disorders. For example, U.S. Pat. No. 4,298,005 to Mutzhas describes a continuous ultraviolet lamp with cosmetic, photobiological, and photochemical applications. A treatment based on using the UV portion of the spectrum and its photochemical interaction with the skin is described. The power delivered to the skin using Mutzhas"" lamp is described as 150 W/m2; which does not have a significant effect on skin temperature.
In addition to prior art treatment involving UV light, lasers have been used for dermatological procedures, including Argon lasers, CO2 lasers, Nd(Yag) lasers, Copper vapor lasers, ruby lasers and dye lasers For example, U.S. Pat. No. 4,829,262 to Furumoto, describes a method of constructing a dye laser used in dermatology applications. Two skin conditions which may be treated by laser radiation are external skin irregularities such as local differences in the pigmentation or structure of the skin, and vascular disorders lying deeper under the skin which cause a variety of skin abnormalities including port wine stains, telangiectasias, leg veins and cherry and spider angiomas. Laser treatment of these skin disorders generally includes localized heating of the treatment area by absorption of laser radiation. Heating the skin changes or corrects the skin disorder and causes the full or partial disappearance of the skin abnormality.
Certain external disorders such as pigmented lesions can also be treated by heating the skin very fast to a high enough temperature to evaporate parts of the skin. Deeper-lying vascular disorders are more typically treated by heating the blood to a high enough temperature to cause it to coagulate. The disorder will then eventually disappear. To control the treatment depth a pulsed radiation source is often used. The depth the heat penetrates in the blood vessel is controlled by controlling the pulse width of the radiation source. The adsorption and scattering coefficients of the skin also affect the heat penetration. These coefficients are a function of the constituents of skin and the wavelength of the radiation. Specifically, the absorption coefficient of light in the epidermis and dermis tends to be a slowly varying, monotonically decreasing function of wavelength. Thus, the wavelength of the light should be chosen so that the absorption coefficient is optimized for the particular skin condition and vessel size being treated.
The effectiveness of lasers for applications such as tattoo removal and removal of birth and age marks is diminished because lasers are monochromatic. A laser of a given wavelength may be effectively used to treat a first type of skin pigmentation disorder, but if the specific wavelength of the laser is not absorbed efficiently by skin having a second type of disorder, it will be ineffective for the second type of skin disorder. Also, lasers are usually complicated, expensive to manufacture, large for the amount of power delivered, unreliable and difficult to maintain.
The wavelength of the light also affects vascular disorder treatment because blood content in the vicinity of the vascular disorders varies, and blood content affects the absorption coefficient of the treatment area. Oxyhemoglobin is the main chromophore which controls the optical properties of blood and has strong absorption bands in the visible region. More particularly, the strongest absorption peak of oxyhemoglobin occurs at 418 nm and has a band-width of 60 nm. Two additional absorption peaks with lower absorption coefficients occur at 542 and 577 nm. The total band-width of these two peaks is on the order of 100 nm. Additionally, light in the wavelength range of 500 to 600 nm is desirable for the treatment of blood vessel disorders of the skin since it is absorbed by the blood and penetrates through the skin. Longer wavelengths up to 1000 nm are also effective since they can penetrate deeper into the skin, heat the surrounding tissue and, if the pulse-width is long enough, contribute to heating the blood vessel by thermal conductivity. Also, longer wavelengths are effective for treatment of larger diameter vessels because the lower absorption coefficient is compensated for by the longer path of light in the vessel.
Accordingly, a wide band electromagnetic radiation source that covers the near UV and the visible portion of the spectrum would be desirable for treatment of external skin and vascular disorders. The overall range of wavelengths of the light source should be sufficient to optimize treatment for any of a number of applications. Such a therapeutic electromagnetic radiation device should also be capable of providing an optimal wavelength range within the overall range for the specific disorder being treated. The intensity of the light should be sufficient to cause the required thermal effect by raising the temperature of the treatment area to the required temperature. Also, the pulse-width should be variable over a wide enough range so as to achieve the optimal penetration depth for each application. Therefore, it is desirable to provide a light source having a wide range of wavelengths, which can be selected according to the required skin treatment, with a controlled pulse-width and a high enough energy density for application to the affected area.
Pulsed non-laser type light sources such as linear flashlamps provide these benefits. The intensity of the emitted light can be made high enough to achieve the required thermal effects. The pulse-width can be varied over a wide range so that control of thermal depth penetration can be accomplished. The typical spectrum covers the visible and ultraviolet range and the optical bands most effective for specific applications can be selected, or enhanced using fluorescent materials. Moreover, non-laser type light sources such as flashlamps are much simpler and easier to manufacture than lasers, are significantly less expensive for the same output power and have the potential of being more efficient and more reliable. They have a wide spectral range that can be optimized for a variety of specific skin treatment applications. These sources also have a pulse length that can be varied over a wide range which is critical for the different types of skin treatments.
In addition to being used for treating skin disorders, lasers have been used for invasive medical procedures such as lithotripsy and removal of blood vessel blockage. In such invasive procedures laser light is coupled to optical fibers and delivered through the fiber to the treatment area. In lithotripsy the fiber delivers light from a pulsed laser to a kidney or gallstone and the light interaction with the stone creates a shock wave which pulverizes the stone. To remove blood vessel blockage the light is coupled to the blockage by the fiber and disintegrates the blockage. In either case the shortcomings of lasers discussed above with respect to laser skin treatment are present. Accordingly, a treatment device for lithotripsy and blockage removal utilizing a flashlamp would be desirable.
To effectively treat an area the light from the source must be focussed on the treatment area. Coupling pulsed laser light into optical fibers in medicine is quite common. The prior art describes coupling isotropic incoherent point sources such as CW lamps into small optical fibers. For example, U.S. Pat. No. 4,757,431, issued Jul. 12, 1988, to Cross, et al. discloses a method for focusing incoherent point sources with small filaments or an arc lamp with an electrode separation of 2 mm into a small area. Point (or small) sources are relatively easy to focus without large losses in energy because of the small size of the source. Also, U.S. Pat. No. 4,022,534, issued May 10, 1977, to Kishner discloses light produced by a flash tube and the collection of only a small portion of the light emitted by the tube into an optical fiber.
However, the large dimension of an extended source such as a flashlamp makes it difficult to focus large fractions of its energy into small area. Coupling into optical fibers is even more difficult since not only must a high energy density be achieved, but the angular distribution of the light has to be such that trapping in the optical fiber can be accomplished. Thus, it is desirable to have a system for coupling the output of a high intensity, extended, pulsed light source into an optical fiber.
Hair can be removed permanently for cosmetic reasons by various methods, for example, by heating the hair and the hair follicle to a high enough temperature that results in their coagulation. It is known that blood is coagulated when heated to temperatures of the order of 70xc2x0 C. Similarly, heating of the epidermis, the hair and the hair follicle to temperatures of the same order of magnitude will also cause their coagulation and will result in permanent removal of the hair.
One common method of hair removal, often called electrolysis, is based on the use of xe2x80x9celectric needlesxe2x80x9d that are applied to each individual hair. An electrical current is applied to each hair through the needle. The current heats the hair, causes its carbonization and also causes coagulation of the tissue next to the hair and some coagulation of the micro vessels that feed the hair follicle.
While the electrical needle method can remove hair permanently or long term, its use is practically limited because the treatment is painful and the procedure is generally tedious and lengthy.
Light can also be used effectively to remove hair. For example, other prior art methods of hair removal involve the application of pulsed light, generally from coherent sources such as lasers. R. A. Harte, et al., in U.S. Pat. No. 3,693,623, and C. Block, in U.S. Pat. No. 3,834,391, teach to remove hair by coagulating single hair with a light coupled to the individual hair by an optical fiber at the immediate vicinity of the hair. Similarly, R. G. Meyer, in U.S. Pat. No. 3,538,919, removes hair on a hair by hair basis using energy from a pulsed laser. Similar inventions using small fibers are described in U.S. Pat. No. 4,388,924 to H. Weissman, et al. and U.S. Pat. No. 4,617,926 to A. Sutton. Each of these teach to remove hair one hair at a time, and are thus slow and tedious.
U.S. Pat. No. 5,226,907, to N. Tankovich, describes a hair removal method based on the use of a material that coats the hair and hair follicle. The coating material enhances absorption of energy by the follicles, either by matching the frequency of a light source to the absorption frequency of the material, or by photochemical reaction. In either case the light source is a laser. One deficiency of such a method and apparatus is that lasers can be expensive and subject to stringent regulations. Additionally, the coating material must be applied only to the hair follicles, to insure proper hair removal and to prevent damage of other tissue.
Light (electromagnetic) energy used to remove hair must have a fluence such that sufficient energy will be absorbed by the hair and the hair follicle to raise the temperature to the desired value. However, if the light is applied to the surface of the skin other than at the precise location of a hair follicle, the light will also heat the skin to coagulation temperature and induce a burn in the skin.
Accordingly, it is desirable to be able to treat the skin by effectively heating multiple follicles, without burning the surrounding skin. Such a method and apparatus should be able to remove more than one hair at a time, and preferably over a wide area of skin, for example at least two square centimeters. Additionally, the method and apparatus should be capable of using incoherent light.
According to a first embodiment of the invention a therapeutic treatment device comprises a housing and an incoherent light source, suitably a flashlamp, operable to provide a pulsed light output for treatment, disposed in the housing. The housing has an opening and is suitable for being disposed adjacent a skin treatment area. A reflector is mounted within the housing proximate the light source, and at least one optical filter is mounted proximate the opening in the housing. An iris is mounted coextensively with the opening. Power to the lamp is provided by a variable pulse width forming circuit. Thus, the treatment device provides controlled density, filtered, pulsed light output through an opening in the housing to a skin area for treatment.
According to a second embodiment of the invention a method of treatment with light energy comprises the steps of providing a high power, pulsed light output from a non-laser, incoherent light source and directing the pulsed light output to a treatment area. The pulse width of the light output is controlled and focussed so that the power density of the light is controlled. Also, the light is filtered to control the spectrum of the light.
According to a third embodiment of the invention a coupler comprises an incoherent light source such as a toroidal flashlamp. A reflector is disposed around the incoherent light source and at least one optical fiber or light guide. The fiber has an end disposed within the reflector. This end collects the light from the circular lamp. In a similar coupling configuration fibers may be provided, along with a linear to circular fiber transfer unit disposed to receive light from the light source and provide light to the optical fibers. The reflector has an elliptical cross-section in a plane parallel to the axis of the linear flash tube, and the linear flash tube is located at one focus of the ellipse while the linear to circular transfer unit is located at the other focus of the ellipse.
The invention further includes the method of treating the skin to remove hair from an an area of tissue by producing electromagnetic energy and applying the energy to the skin. At least one pulse of incoherent electromagnetic energy is preferably used. The incoherent electromagnetic energy is then coupled to an area of the surface of the tissue that includes more than one hair follicle.
Additionally, in one alternative embodiment the energy may, but not necessarily, be produced by pulsing a flashlamp to generate a pulse having an energy fluence on the order of 10 to 100 J/cm2. The energy can be coupled through a window in a housing in which the flashlamp is located, by reflecting the energy to the tissue through the window and through a gel located on a surface of the tissue. The window may be brought into contact with the gel. In other alternative embodiments the angular divergence of the electromagnetic energy is controlled, and thus the depth of penetration into the tissue, and the coupling to the hair and to the hair follicles, is also controlled. In another alternative embodiment each step of the method is repeated, but at least two angular divergences are used, thus obtaining at least two depths of penetration.
In other alternative embodiments, electromagnetic energy is filtered. Specifically, in one embodiment the electromagnetic energy is filtered according to the pigmentation level of the tissue to be treated. In another alternative, energy that has a wavelength of less than 550 nm and greater than 1300 nm is filtered. Some or all of such energy can be filtered.
In yet another alternative embodiment, the pulse produced has a width of less than 200 msec, and/or the delay between pulses is on the order of 10 to 100 msec between the pulses. In one embodiment, the surface area of the energy at the tissue is at least two square centimeters.
In accordance with a second aspect of the invention an apparatus for removing hair from an area of tissue that includes more than one hair follicle includes a source of pulsed incoherent electromagnetic energy. The source is located within a housing, and a coupler directs the incoherent electromagnetic energy to the surface of the tissue.
According to an alternative embodiment the source is a flashlamp and a pulse generating circuit that generates pulses of energy that have an energy fluence on the order of 10 to 100 J/cm2. The coupler can include a transparent window and the housing a reflective interior, wherein the energy is reflected to the window. A gel is disposed on the surface of the tissue and the window is in contact with the gel, to couple the energy through the window and gel to the surface of the tissue. In another alternative embodiment the energy provided by the coupler has a range of angular divergences.
In another alternative embodiment at least one band pass electromagnetic filter is disposed between the source and the tissue. The filter can be selected such that the wavelength of the energy that passes through the filter is based on the pigmentation level of the treated tissue. Alternatively, the filters pass energy that has a wavelength of between 550 nm and 1300 nm.
In other embodiments, the source provides pulses having a width of less than 200 msec, and/or delays between pulses on the order of 10 to 100 msec. In another embodiment, the area of the energy at the tissue is at least two square centimeters.
According to a third aspect of the invention, a method of removing hair from an area of tissue that has more than one hair follicle includes producing at least one pulse of electromagnetic energy. A gel on a surface of the tissue cools the tissue, but the gel is not adjacent the hair follicle. The electromagnetic energy is coupled to the surface of the tissue.
In one alternative embodiment, the energy is produced by pulsing a flashlamp, and a pulse having an energy fluence on the order of 10 to 100 J/cm2 is thereby generated. In another embodiment, the flashlamp is located in a housing that includes a transparent window and the energy is reflected through the window and directed through the gel to the tissue. In yet another alternative embodiment, the angular divergence of the electromagnetic energy is selected to determine the depth of penetration into the tissue, and to determine the coupling to the hair and to the hair follicles. Also, each step of the method may be repeated using at least two different angular divergences, whereby at least two depths of penetration are obtained.
In another alternative embodiment, the electromagnetic energy is filtered. The filtering can be done in accordance with the pigmentation level of the treated tissue. Alternatively, filtering may include filtering some or all of the energy that has a wavelength of less than 550 nm and greater than 1300 nm.
In another alternative embodiment pulses produced have a width of less than 200 msec. The delay between pulses may be on the order of 10 to 100 msec. Also, the area of the energy at the tissue can be large, for example more than two square centimeters. The energy may be incoherent, such as that produced by a flashlamp for example, or coherent, such as that produced by a laser, for example.
In accordance with another aspect of the invention, an apparatus for removing hair from an area of tissue that has more than one hair includes a source of pulsed electromagnetic energy. A gel is disposed on the surface of the tissue such that the gel cools the tissue but is not adjacent, and does not cool, the hair follicle. A coupler is disposed between the source and the surface to couple the energy to the surface.
In one alternative embodiment, the source is a pulsed flashlamp that generates pulses having an energy fluence on the order of 10 to 100 J/cm2. In another alternative, the flashlamp is located in a housing that includes a transparent window and a reflective interior. In yet another alternative embodiment the shape of the coupler determines the angular divergence of the electromagnetic energy, which determines the depth of penetration of the energy into the tissue, and determines the coupling to the hair and to the hair follicles. The apparatus may include a band-pass filter disposed between the source and the surface. In one alternative the band-pass filter passes energy having a wavelength of between 550 nm and 1300 nm. The source may be a source of incoherent energy, or a source of coherent energy, such as a laser, for example.